Food Allergies in Dogs

Key Takeaways

Food allergies occur when the immune system overreacts to an ingested protein.

• The most common food allergens in dogs are animal proteins such as beef, chicken, eggs, and dairy products

• The most common symptom of food allergies in dogs is severe itchiness of the skin. Approximately 30% of dogs with food allergies show gastrointestinal symptoms

• The only way to diagnose food allergies is through a food elimination trial, where the dog is fed a hypoallergenic diet for 6-8 weeks

• Trialing different proteins over time allows owners to see if their dog’s symptoms return in response to a specific protein

• Based on these findings, a list of allergens is made, and an appropriate, allergen-free diet is selected for that dog

A Closer Look: What Are Food Allergies in Dogs?

Food allergies are difficult to diagnose, and identifying the specific allergen that the dog reacts to is often a time-consuming process. Once the allergen has been identified, most dogs recover completely once the allergen has been removed from their diet. 

The most common symptom of food allergies is severe itchiness of the skin, but symptoms such as diarrhea, vomiting, flatulence, and abdominal pain occur in some cases. Dogs showing these symptoms require prompt veterinary care.

Risk Factors

Food allergies are uncommon in dogs. Itchy skin and symptoms of digestive upset are usually caused by other conditions. Studies suggest that only 1-2% of dogs develop food allergies in their lifetime. Once the skin is inflamed and itchy, dogs with food allergies commonly develop infections of the ears and skin. Symptoms of these infections include:

• Head shaking • Scratching at the affected ear • Redness and swelling • Dark discharge from the affected ear

• Foul odor • Weeping, open sores • Pus or blood oozing from the skin

Dogs showing these symptoms require prompt veterinary attention.

Possible Causes

Food allergies occur when the immune system overreacts to an ingested allergen. The reason the immune system overreacts is unknown. Some breeds are predisposed to allergies.  The most common food allergens are animal proteins, including: 

• Beef • Chicken • Eggs • Dairy products

Allergies to grains are rare. Gluten allergies have only been reported in Irish Setters and border terriers.

Main Symptoms

Food allergies have two main groups of symptoms: skin reactions and gastrointestinal reactions. Many dogs have both types of symptoms, but skin reactions are most common.  The most common symptom of food allergies is severe itchiness, particularly affecting the rump, armpits, face, groin, and between the toes. Other common skin symptoms include:

• Reddening, swelling, or crusting of the skin • Hair loss • Scrapes or scratches from itching • Hives

• Darkening and thickening of the skin

Only 30% of food-allergic dogs show gastrointestinal signs. Symptoms include:

DiarrheaVomiting • Flatulence • Abdominal pain

Testing and Diagnosis

Diagnosing a food allergy is difficult, as there are many potential causes of itchiness. An extensive history is taken to identify when symptoms began, what symptoms are occurring, and whether there are any trends. A physical examination also provides information to the veterinarian about the dog’s condition. 

The veterinarian may choose to run tests to rule-out other causes of itch. If a food allergy is suspected, a food elimination trial is recommended. Food elimination trials are the only definitive test to diagnose food allergies. Allergy tests on blood, hair, or saliva are not effective at diagnosing food allergies in dogs. 

To conduct a food elimination trial, the dog is fed a hypoallergenic diet that is specifically designed for these types of trials. There are two main types of hypoallergenic diets:

Novel protein: These diets are made of proteins that the dog is unlikely to have eaten before. Examples include kangaroo, elk, alligator, bison, or ostrich.

Hydrolyzed protein: These diets are processed to break apart proteins into small compounds that the immune system does not recognize. 

Although many commercial diets are advertised as hypoallergenic, only veterinary prescription diets are acceptable for elimination trials. Prescription diets have strict cross-contamination regulations that prevent any potentially allergenic proteins from entering the prescription food. Other commercial diets are not required to follow these strict protocols. 

In a food elimination trial, the suggested diet is fed for a minimum of 6-8 weeks, to see if symptoms are reduced or resolve. During this period, the dog cannot eat any foods not approved by their veterinarian, including treats, table scraps, flavored medications, and supplements. 

If symptoms resolve with a hypoallergenic diet, then a food allergy is suspected. To truly confirm the diagnosis, the previous food is reintroduced to see if symptoms return. This trial period lasts up to 10 days. Through repeated testing, a list of allergens for that particular dog is made.

Steps to Recovery

Drugs that reduce itchiness are helpful in some cases, to help prevent the dog from causing further damage to their skin while the diet trial is occurring. Dogs with skin infections often require antibiotics or antifungal medications as well. 

Allergies are a life-long condition. With diet trials, an appropriate, allergen-free diet is determined for each patient. Removing the allergen from the diet usually resolves symptoms completely. Occasionally, dogs develop new food allergies, which require new food elimination trials. 

Dogs that do not respond completely to removing food allergens may have other allergic conditions as well. Up to 30% of dogs with food allergies have atopic dermatitis or flea allergy dermatitis in addition to their food allergies. These allergies require additional treatment for symptoms to resolve.


Food allergies are not contagious. Since the root cause of allergies is unknown, there is no way to prevent them from developing, but identification of allergens and completely removing them from the diet should resolve symptoms completely. 

Many pet parents choose to rotate their dog’s diet frequently, exposing them to many different animal proteins. Some owners believe this helps prevent allergies. There is no evidence to support this belief, and the practice of rotating food ingredients makes it more difficult to find a novel protein source if the dog develops allergies. Therefore, it is not recommended to rotate protein sources for dogs.

Are Food Allergies Common in Dogs?

Food allergies are uncommon in dogs. Only 1-2% of dogs develop food allergies.

Typical Treatment

• Diet elimination trial • Anti-itch medications

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